Which extra-embryonic membrane is used by mammals to form part of the placenta?
A -The yolk sac
B - The chorion
C - The allantois
D - The amnion
E - None of them
Answer: B - The chorion
Which extra-embryonic membrane is used by mammals to form part of the placenta?
A -The yolk sac
B - The chorion
C - The allantois
D - The amnion
E - None of them
Answer: B - The chorion